When digging a typical well, well drillers usually use a tool that utilizes augered flighting, so that when the tool is moved into engagement with the surface of the earth and rotated the auger moves the tool into the earth and removes the surrounding material to the surface of the earth. This forms an open well shaft in the earth. When the well shaft is completed, the augered tool is removed from the well shaft and well casing and internal components can be built into the excavated shaft formed by the augered tool.
Once the well bore is drilled, the driller installs well casing and well screens and fills the annulus around the casing with a gravel (filter) pack. The gravel pack prevents sand and fine particles from moving from the aquifer formation into the well.
At the surface of the well, a surface casing is commonly installed to facilitate the installation of the well seal. The surface casing and well seal protect the well against contamination of the gravel pack and keep shallow materials from caving into the well.
It is problematic that the excavated well shaft will collapse if the surrounding soil is not stable. When the well shaft is to be excavated at an angle other than vertical, there is even a greater risk of well collapse due to gravity. To avoid a well collapse, well drillers often use drilling fluids such as bentonite to help maintain the shape and integrity of the shaft. Also, the excavated well usually develops debris during the digging activities that tends to fall into the excavated shaft that may form an obstruction to placement of the well casing into the well excavated shaft. Well drillers usually must remove the debris from the excavated shaft before the well casing is placed in its final position within the shaft. To remove the debris well drillers typically use fluids that circulate in the excavated well shaft. Use of these materials and the associated labor increase the costs of the well installation, and in some situations may cause the well drillers to move the site of the well.